This something to be aware of with non contact IR temperature indicators.
The issue was the IR device was not giving the correct temperature reading of hot oil, reading low.
Each device is made a little different depending on the distance that the device will read accurately. Mine is 36 cm (~14 inches). But most have the same technology of a lens to focus the reflected IR energy upon the IR detector in the unit.
What I discovered was the Fresnel lens had a layer of oil film that was absorbing reflected IR energy (scattering and not focusing) as well as reading the local temperature at the lens.
I cleaned the lens and the unit temperature is now correct.
Moral of this story is to keep the IR lens clean.
Chris